Separation and recovery process



SEPARATION AND RECOVERY PROCESS NOV. 19,1963

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The present invention relates to a novel process for separation and recovery of components from mixtures. comprising hydrogen, hydrogen halides, boron trihalide, and haloboron hydrides, and which may also contain diborane. More particularly, the invention relates to separation and recovery-of components of reaction product mixtures obtained by reacting boron trichloride with hydrogen to provide mixtures of chloroboron hydrides,

boron trichloride, hydrogen chloride, hydrogen and diborane, such as may be produced from processes described in 'copending applications, Serial No. 744,348, filed June 25, 1958, and Serial No. 748,156, filed July 14, 1958, entitled Preparation of Boron Compounds.

In broad aspect, the invention embodied herein comprises (1) subjecting a substantially anhydrous mixture comprising haloboron hydride, hydrogen, hydrogen halide and boron trihalideand which mixture may also contain diborane, to contact with an organic sulfide from the group consisting of aryl and alkyl aryl sulfide that selectively complexes the boron-containing compounds in said mixture without complexing the hydrogen halide and hydrogen, (2) dissociating the resulting complex to liberate the boron-containing compounds, (3) disproportionating the Uted States Patent ,.mix ture of liberated boron-containing compounds from a (2) to a mixture of diborane and boron trihalidefr'o'm which the diborane is separated, and (4) separating the mixture of hydrogen and hydrogen halide (from step (1)) into its components. In reference to step (4), such a separation can be effected by any of several means and, for example, by passing the mixture of hydrogen and hydrogen halide through an aqueous medium (e.g., water) whereby the hydrogen halide is absorbed. In another embodiment, the mixture of hydrogen and hydrogen halide can be contacted with a suitable metal halide in combination with a suitable ether or alkylaryl hydrocarbon, as defined more fully hereinatfer, to selectively complex the hydrogen halide and, following removal of the uncomplexed hydrogen, dissociating the complex of the hydrogen halide with said metal halide and ether or alltylaromatic hydrocarbon to liberate the hydrogen halide. In a continuous process, the sulfide liberated in step (2) is re cycled to step (1).

In order to further describe the process embodied herein, reference is made to the accompanying flow sheet which, for purposes of illustration and not limitation, illustrates an embodiment of the process with specific utilization of the starting mixtures and reactants shown in the flow sheet.

A feed mixture comprising B H BHCl BCl HCl and H is passed into vessel 1 via line 10 into which diphenyl sulfide is fed via line 11. In vessel '1, the feed mixture contacts the diphenyl sulfide whereupon the latter selectively complexes all of the boron-containing compounds in the feed to form a diphenyl sulfide complex of 'BHClg, of SCI; and of B H which is withdrawn from vessel 1 via line 12, the mixture of H and HCl which is not complexed being withdrawn via line 13 from vessel 1. The complexes of the diphenylsulfide and boron-containing compounds in line 12 are subjected to a. dissociation treatment in vessel 3 whereby the diphenyl sulfide is liberated and recycled to vessel 1 via line 11. The liberated mixture of boron-containing compounds is withdrawn from dissociation tower 3 via line 14 and passed 3,111,373 Patented Nov. 19, 1963 to distillation tower '5 wherein the mixture is disproportionated to form B ll and BCl the BCl being withdrawn via line 15 as the residue from the disproportionating treatment in tower 5 and the B H as the distillate via line 16. The mixture of H -HCl in line 13 is passed into vessel 2 to which is fed, via line 17, a suitable metal halide (e.g., M0,) in mixture with an ether or an alkylaromatic hydrocarbon (eg.-, meta-xylene).

In vessel 2, the HCl in the HCl--H mixture is selectively complexed by the Alcl -meta-xylene complex, and the hydrogen is withdrawn via line 18, and the complex of the HQ with the metal halide-meta-xylene is removed via line 19. 'lhe latter complex passed into tower 4, is

dissociated toliberate the vHCl which is removed via line 20, and the liberated aluminum chloride meta-xylene is recycled via line 21 to line 17 into tower- 2. In such a. manner, the components of the starting feed material introduced into vessel 1 are separated and recovered as valuable products (i.e., diborane, hydrogen, BCl and HCl) and the substances used for effecting such a result, namely the diaryl sulfide (e.g., diphenylsulfide), AlCl and ether or alkylaromatic hydrocarbon (e.g., metaxylene) are also recovered in substantially quantitative and substantially pure form for reuse in the process.

In step,(l), wherein the boron-containing components are selectively complexed with the organic sulfide, the starting mixture is contacted with the sulfide in an amount substantially stoichiometrically equivalent to, or in excess of (such as up to about seven molar equivalents or more of the sulfide) the amount required to complex the boroncontaining compounds present in the starting mixture. Preferably, diphenyl sulfide is used as the diaryl sulfide.

However. other sulfides such as ditolyl sulfide, phenyl tolyl the sulfide complexes at the temperature employed.

I In step(2), wherein the complex of the sulfide with the boron-containing compounds is subjected to dissociation, the dissociation may be accomplished by heating the complex to a temperature of from about 40 to 200 C., and preferably, from about 50 to 70 C. as, at such tem peratures, substantially quantitative recovery of substantially pure sulfide and boron containing compounds is effected. The liberated boron-containing compounds (e.g., B H BHCl and BCl subjected to disproportionation wherein, for example, the BBQ: disproportionates to B H and HG; are so converted (i.e., step (3)) by heating, such as by use of total reflux in a fractionation column and, for examplqfrom about 0 to about 50 C., followed by distillation to separate the B H from BCl The distillation treatment, for example, can be effectively carried out at two atmospheres pressure with reflux at about 0 C.

In step (4), wherein the l l HCl mixture from step (I) is separated into its components by use of the embodiment described with reference to the drawing, the mixture is contacted with a suitable metal halide in combination with an ether or an alkylaromatic hydrocarbon, the HCl certain elements from group ill-A, lV-A and V-A of the periodic table, and ferric chloride, in presence of a suitable organic solvent, including others. such as aliphatic ethers, chlorinated aliphatic ethcrs, aliphatic arumatic' ethers, dialiphatic sulfides, aliphatic aromatic sulfides, etc. as well as certain hydrocarbons such as thealkyluryl hydrocarbons. In general,. the ethers used for this purpose may be designated by the formula wherein Z is an element of group Vl-A, i.e., oxygen. sulfur, selenium and tcllurium, and which ethers have a Volatility substantially lower than that of any gas in admixture with the HCl tobe selectively complexcd. lreferred are such ethers containing an aliphatic group of up to six carbon atoms as in dimethyl ether, diethyl ether, diisopropyl ether, dibutyl ether, diisobutyl ether, dihcxyl ether, and others. 'Halogenated aliphatic thers are likewise useful, as for example, bis-z-chloroethyl ethcr, bis- 3-chloropropyl ether, etc. as well as certain alkylaryl ethers such as anisole, phenetole, and others. Sullides, such as dialkyl sulfide and alkylaryl sulfides, may also be used. Such sulfides are those corresponding to the aforesaid oxygen-containing ethers except that the oxygen is replaced with sulfur. Also useful for such a purpose are alkylaryl hydrocarbons such as toluene, ethylbenzene, the xylenes, mesitylene, the durenes, and, in general, alkyl benzenes containing up to about six carbon atoms in the alkyl substituent.

The Lewis-type acids suitable for the aforesaid purpose are, in addition to ferric chloride and zinc chloride,

the halides of certain elements from group III-A, group 1V-A, and group VA of the periodic table.v Examples of such metal halides include BF BCl AlCl GaCl InCl TlCl SnCl PbCl SbCl and AsCl substances such stannic chloride and aluminum chloride being preferred.

For the selective. complexiug of, for example, the HCl from the H -HCl mixture, the amount of the complexing agent that is used in proportion to the solvent (e.g., ether,

present in the starting taining compounds. Thus, and when diborane is also mixture, it complexes with the diaryl sulfide to provide a weaker complex than that formed with. the boron halides and haloboron hydrides. Such a complex may, however, be dissociated quantitativcly without decomposition to liberate the diborane. 1 On the other hand, the diborane complex with diahphatrc sulfides decompo'ss'iiicomplet'ely and only a portion of the diborane is liberated.

In order to still further describe the invention, the following embodiments are set forth for purposes of illustration and not limitation.

Example I A gaseous reaction mixture (273.1 mmoles) composed essentially of 92.7% H 3.9% BCl 1.6% BHCI 1.6%

' HCl and a trace amount of diborane, was maintained at under reduced pressure (10 mm.) whereby BHCI; and e room*tcnrperatureand a pressure of 825 mm Hg. The

gaseous mixture was-bubbled through a solution at 0 C. i

BCl were generated. Hydrolysis of the diphenyl sulfidedesorbate and the etlluent gas condensate, followed by determination of the hydrogen evolved, gave the results shown in the following-table:

' Diphenyl Efiluent --:-Inltlal"l\tfixturc 1 sulfide Gas desorbate BVls 10. 76 9. 26 1. 5 40 Brion 4.34 4.34 0.0

H01 4. 34 0. 0 4. 34 T-la 253 0. 0

thioether, alkylaromatic hydrocarbon) is such that the hydrogen chloride is complexed but, preferably, the amount ofthe complexing agent and solvent is controlled such as to complex substantially all of the hydrogen chloride while obviating or minimizing the use of substantial excess of the complexing agent and solvent and of the latter two substances an excess of the solvent is, in most cases, not particularly disadvantageous.

The complex formation of, for example, the HCl can be carried out at temperatures up to about room temperature; that is, up to about 25 C. but, preferably, at substantially lower temperatures such as about 0 C. with particularly suitable results being obtained by use of temperatures of from about 30 C. to about 0 C. The complex formation can be carried out at any pressure higher than the dissociation pressure of the complex at the temperature employed.

The complex formed with the hydrogen chloride is treated, for liberation of the BC], by heating the complex. That is, the complex can be heated to from about to about 200 C. with a more preferred temperature being from 75 to about 150 C. Any pressure may be used which is lower than the dissociation pressure of the complex at the temperature being used for the desorption. However, a preferred method is to employ pres sures of approximately one atmosphere or lower in order to avoid excessive temperatures. the complex is heated to a temperature sufficientto cause tfiesorption of the hydrogen halide in substantially pure orm.

In practice of this invention, and in reference to step (1) the use of the aforesaid sulfides rather than dialiphatic sulfides provides markedly improved results as the use of dialiph-atic sulfides decompose extensively during thermat dissociation of thc complex thereof with boron-com In general, however,

1 Quantities are expressed in nilllirnoles.

The BCl and BHCl desorbed from the diphenyl sulfide were condensed as a liquid at 0 C. and heated under 2 atmospheres pressure to disproportionate the BHCl as follows:

7.58 millimoles anhydrous ferric chloride and 5.0 ml. B,B-

dichloroethyl ether held at 0 C. The efiluent gas was scrubbed with distilled water, and found to contain 1.96 millimoles HCl as shown by titration of the scrubbing water with standard alkali. The ferricchloride etherate solution containing the complexed hydrogen chloride was then attached to a vacuum apparatus. Heating and evacuatingat 70 C. for about one hour, and passing the gas evolved through traps maintained at and -196 C. resulted in the recovery of 9.44 millimolcs of pure hydrogen chloride (vapor tension l25 mm; at -l12 C.) as a condensate in the --l96 trap. The observed high ratio of HCl/FeCl in solution (9.44/7.58=1.24) was attributed to the solubility of hydrogen chloride in the 5,5- dichloroethyl ether in addition to complex formation.

, 5 v Example II of sulfide complexes from step (t) to liberate the sulfide and a mixture of the boron-containing components, (3)

. thermally disproportionating ata temp Q from there was used 21.5 moles of dlphenyl sulfide and S.l about to abomSOo C" the mixture f b o -containing grams of the saturated aliphatic hydrocarbon oil. The i components liberated in step (2) to provide a mixture of results obtained are set forth in the following table. boron trichldride and boron hydridcs d oving by 11 I distillation the boron hydrides from the resulting disproportionated mixture, (4) contacting the mixture of hy- In anotherrun, carried out as described in Example I,

l h D p 3%? about -30 C. up to about 25 C. from step (1) with a Initial Mixture, mllllmoles I sulfide desmbui complex formed by a Lewis acid-type halide selected from the group consisting of halides of boron, aluminum, g-gg -g gallium, indium, thallium, tin, lead, antimony, and ar- 3190 010 3:90 senic, ferric chloride and zinc chloride with a complexing 247 M agent from the group consisting of compounds of the formula R Z when R is hydrocarbon and Z is from the ,zlnthisrun, the diphenyl sulfide desorbate was treated group Consisting Of yg b Sulfur, Selenium and in the manner of that in Example I whereby diborane "tellurillm and (2) alllyl aryl hydrocarbons to selectively was obtained follownig the disproportionation and fracplex the hydrogen chloride, and (5) dissociating by tionation steps. heating at from about 50 to about 200 C. the complex To illustrate the recovery of hydrogen chloride from f the y r g chloride produced in p to liberate the hydrogen stream, a mixture consisting of 8,17 millithe hydrogen chloride from the Lewis acid halide commoles hydrogen chloride and hydrogen was placed in a P19715118 agent liter flask held at 760 mm. Hg and C, Thi mixt 3. A process, as defined in claim 2, wherein the sulfide was treated in the same manner employed in Exampl 1 25 liberated in step (2) is recycled to step (I) and the Lewis except that the complexing reagent was made up to 17.6 acid yp halide and Complexing agent liberated in p miliimoles anhydrous aluminum chloride and 18.2 milliis recycled !0 p moles of mesitylene. The hydrogen chloride was substan- A Process, s defined in Claim erein the Subtiafly r tained s a complex f l v latili ll i h stantially anhydrous mixture initially contains diborane.

hydrogen to pass through the reagent in substantially pure 5. A P P as defined in Claim ei t anform. Desorption of the hydrogen chloride at 100 C. hydrous mixture initially contains diborane, the diaryl/ drogen and hydrogen chloride at a temperature of from with pumping resulted in'the recovery of 87% of that sulfide is diphenyl sulfide, the Lewis acid halide is from qriginally presant i h l the group consisting. of aluminum chloride and ferric While there are above disclosed but a limited number chlm'ider the complexing flgflnt for e wis acid of embodiments of the process of the invention herein 5' halide is f group Consisting Q fLfl'- y a presented, ibis possible tolproduce still, other embodiments ether and mesilyleflewithout departing from the inventive concept herein dis- A Process for Separation and y Of s closed, and it is desired therefore that only such limitations anhydrous mixmfe Comprising z s, EH92, be imposed on the appended claims as are stated therein. HQ and a e which comprises Contacting id mixh i l i 40 ture at below about 25 C. with'diphenylsulfide in an 13A process fo separatign d recovery f Components amount at least stoichiometrically suflicient to selectively of a substantially anhydrous mixture comprising hydrocomplex the boron-Containing p en s in said anhy gen, hydrogen chloride, boron'trichloride and chloroboron drous mixture 0 Pmvide a diphenylsulfide COmPXBX hydrides which comprises (1) contacting said substantially F and a mixture of hydrogen and H61, a g the anhydrous mixture with a diaryl sulfide at temperatures dlphellylsulfidc complex miXlure f m tep (1) to'irom below 5 that selectively complexes the bommcom about 40 to about 100, C. to liberate the diphenylsulfide raining components in said mixture to provide a mixture from the Complex Thereby liberating a mixture of B H of said sulfide complexes of said boron-containing com- BHclz and BCls, dispropol'liofiming t0 z a and ponents and a non-complexed mixture of hydrogen and Bela W f f of a b BHClz and a from p the hydrogen chloride, (2) thermally dissociating at a by sub ecting said mixture to a temperature of from about temperature of from about 40 to 200 C., the mixture to PE With removal-0f z s from f sulfida compkwmitsau) to liberate the sulfide BCl by dlStlllflilOn, (4) recycling to step l) the diphenyland a mixture of the boron-containing components, (3) suifide hberated in Step 2 Contacting the z thermally disproportionating at a temperature from about mlxtflre f P with a complfix formed y (a) Z o to about c the mixture of boromcontaining Lewis acid halide from the group consisting of ferric poncnts liberated in step (2) to provide amixture of boron blonds and aluminum chloride with B c p s trichloride and boron hydrides and removing by distilla- 3 from the grovewnsisfing of mcsitllene and 5 5 tion the boron hydrides from the resulting disproportiorldlchloroethyl etheri'smd HZHCI mixture being contacted ated mixture, and (4) separating by volatilization the hyat a temperature below '25 C. with an amount f drogen from the hydrogen chloride after conversion of said Lewis acid halide P F Sufficient, Complex the hydrogen chloride to a complex in which the partial substanmny an the HC! m Smd mixture, liberating pressure of the hydrogen chloride is substantially neglithe Hcl from W l miXlllrc formed in gible at ordinary temperatures, in the mixture thereof Step (5) by hwtmg Said mixture to from about 50 t0 btained in p (1)., about 200 C., and (7) recycling the liberated Lewis acid 2. A process for separation and recovery of components hahde'complexmg agent fljom Step tO'Si-ep of a substantially anhydrous mixture comprising hydro- A PmCeSF for Sepamuo" and recovery of components gen, hydrogen chloride, boron trichloride and chlorohoronof subsmmmuy mixture Compfising y hyd-rides which comprises (1) Contacting Said substam gen, a hydrogen halide, a boron trihalide and halobororl tially anhydrous mixture with a diaryl sulfide at temperahydridcs which comprises (1) Contacting Said Substantially tures below 50 C. that selectively complexes the boronn anhydrous mixture at a temperature P 0 about 50 C. containing components in said mixture to provide a mixwith an Organic Sulfidc from the group Consisting of W ture of said sulfidecomplexes of said boron-containin and alkyl firyl sulfides that Selectively complexes the components and a non-complexed mixture of hydrogen boron-containing components in said mixture in amount and the hydrogen chloride, (2) thermally dissociating at at least substantially stoichiomctrically sufiicient to co a temperature of from about 40 to 200 C., the mixture '75 plex the boron-containing components in the anhydrous 7 7 a mixture, to provide a mixture of said sulfide complexes of said boron-containing components and a non-complexed mixture of hydrogen and the-hydrogen halide, (2) dissociating the mixture of sulfide complexes from step (I) by heating at from about 40 C. to about 200 C., to liberate the sulfide and a mixture of the boron-containing components, (3) disproportionating the mixture of boroncontaining components liberated in step (2) at from about 0 to 50 C., to provide amixture of boron tri step (1) with a complex formed by a-stoiehiometrically sutlicient amount of a Lewis acid-type halide selected from the group consisting of halides of boron, aluminum, gallium, indium, thallium, tin, lead, antimony, and arsenic, ferric-chloride and zinc chloride with a-complexingagent from the group consisting of compounds designated by the formula R Z wherein Z is an element selected from the group consisting of oxygen, sulfur, selenium, and tellurium, audit is a hydrocarbon radical to selectively com plex the hydrogen halide, and (5) dissociating the complex of the hydrogen halide produced in step (4) by heating at from about 50 to about 200 C., to liberate the hy-.

drogen halide from the Lewis acid. halide complexing agent.

References Cited in the file of this patent OTHER REFERENCES Baber -:-et -al.: General .College Chemistry, 1940, 7

"page 88. 

2. A PROCESS FOR SEPARATION AND RECOVERY OF COMPONENTS OF A SUBSTANTIALLY ANHYDROUS MIXTURE COMPRISING HYDROGEN, HYDROGEN CHLORIDE, BORON TRICHLORIDE AND CHLOROBORON HYDRIDES WHICH COMPRISES (1) CONTACTING SAID SUBSTANTIALLY ANHYDROUS MIXTURE WITH A DIARYL SULFIDE AT TEMPERATURES BELOW 50*C. THAT SELECTEIVELY COMPLEXES THE BORONCONTAINING COMPONENTS IN SAID MIXTURE TO PROVIDE A MIXTURE OF SAID SULFIDE COMPLEXES OF SAID BORON-CONTAINING CONPONENTS AND A NON-COMPLEXED MIXTURE OF HYDROGEN AND THE HYDROGEN CHLORIDE, (2) THERMALLY DISSOCIATING AT A TEMPERATURE OF FROM ABOUT 40 TO 200*C., THE MIXTURE OF SILFIDE COMPLEXES FROM STEP (1) TO LIEBERATE THE SULFIDE AND A MIXTURE OF THE BORON-CONTAINING COMPONETNS, (3) THERMALLY DISPROPORTIONATING AT A TEMPERATURE OF FROM ABOUT 0* TO ABOUT 50*C., THE MIXTURE OF BORON-CONTAINING CONPONENTS LIBERATED IN STEP (2) TO PROVIDE A MIXTURE OF BORON TRICHLORIDE AND BORON HYDRIDES FROM THE RESULING DISPROPORTIONEATED MIXTURE, (4) CONTACTING THE MIXTURE OF HYDROGEN AND HYDROGEN CHLORIDE AT A TEMPERATURE OF FROM ABOUT -30*C. UP TO BOUT 25*C. FROM STEP (1) WITH A COMPLEX FORMED BY A LEWIS ACID-TYPE HALIDE SELECTED FROM THE GROUP CONSISTING OF COMPOUNDS OF THE FORMULA R2Z WHEN R IS HYDROCARBON AND Z IS FROM THE GROUP CONSISTING OF (1) OXYGEN, SULFUR, SELENIUM AND TELLURIUM AND (2) ALKYL ARYL HYDROCARBONS TO SELECTIVELY COMPLEX THE HYDROGEN CHLORIDE, AND (5) DISSOCIATING BY HEATING AT FROM ABOUT 50 TO ABOUT 200*C. THE COMPLEX OF THE HYDROGEN CHLORIDE PRODUCED IN STEP (4) TO LIEBERATE THE HYDROGEN CHLORIDE FROMTHE LIEW ACID HALIDE COMPLEXING AGENT. 